The invention of this application relates to the subject matter of our U.S. Pat. No. 5,042,441, issued Aug. 27, 1991 entitled xe2x80x9cLow Emission Combustion System For Internal Combustion Engines,xe2x80x9d and U.S. Pat. No. 5,081,961, issued Jan. 21, 1992 entitled, xe2x80x9cInternal Combustion Engine With Rotary Exhaust Control.xe2x80x9d The referenced patents describe opposed piston engines that are capable of generating enormous power densities by a design that can achieve ultra-high compression/combustion pressures of over 300 bars. When the opposed piston engine designs are associated with auxiliary super-charging or turbo-charging systems to create a five, ten and fifteen atmospheric boost, a tremendous thermal energy density per cycle can be achieved.
This ability to generate an unprecedented power density in an engine device provides the opportunity to incorporate internal co-generation using a Rankin cycle combined with an internal air cooling cycle with thermal recovery and regeneration in association with and coincident with the internal combustion cycle. This integration of cycles forms a total energy thermal cycle or a xe2x80x9ctriple cyclexe2x80x9d operating system.
In a conventional internal combustion engine the operating cycle is usually associated with an energy balance made up of 30% thermal efficiency, 30% cooling energy rejection, 30% exhaust energy and 10% friction.
At very high levels of air charging, where the air charge is boosted at 5, 10 or 15 bars, the thermal energy to be rejected by cooling and exhaust reaches an intensity that threatens the integrity of the structural components of the engine. Normal cooling by transferring excess heat through cylinder walls to a cooling system is inadequate to prevent thermal stresses in the cylinder and exhaust components of the hyper-charged engine.
Conventional cooling technologies cannot manage the combined thermal stress and mechanical stress generated by the ultra high pressure and ultra high power density which the opposed piston engine designs, in particular, are capable of producing.
However, novel cooling techniques and controlled injection processes described in this application permit a controlled combustion and a regenerative and cogenerative cooling.
This invention relates to a controlled injection process and a combined cycle cooling process for internal combustion engines for minimizing thermal losses and mechanical losses in high pressure reciprocal engines.
In an engine of the general type, having an ultra high energy density, it is desirable to have a cooling system that has the capability to work in an internal regeneration/cogeneration mode, where thermal energy extracted during cooling is recovered as useful power. The xe2x80x9ctriple cyclexe2x80x9d cooling system of this invention uses a regenerative air charge to cool the cylinder liner and a water injection to drive the air charge and cogenerate energy in a Rankin cycle.
In a preferred embodiment, the engine cylinder is surrounded by a cylindrical and concentric air-gap form an annular volume with a first mission to forming an insulating thermal barrier or air jacket. In the compression stroke a part of the compressed air invades this annular insulating volume. The compressed air absorbs a part of the heat transferred through the internal wall or liner of the cylinder. At the end of compression and coincident with the time of fuel injection, high-pressure, pure water is tangentially injected at the bottom of the air-gap. The high circular speed of convection and conversion to steam absorbs the rest of the excess thermal energy, transforming this heat into high-pressure, internally cogenerated steam. This steam pushes the heated air back into the combustion chamber of the engine. The compressed air, pre-heated and tangentially re-injected into the combustion chamber during the process of combustion, produces major improvements in completing combustion and increasing the thermal efficiency of the engine. The compressed air is followed by the injection of steam during the same combustion process, the final result being a combined working fluid formed from combustion gases, heat regenerating compressed air, and cogenerating steam. The total energy, triple thermal cycle has a potential for a maximum thermal efficiency of 80-90%. The super high turbulence produced by the tangentially re-injected, high-speed and high-pressure air, and the associated injected steam has a major effect in producing a super clean combustion, with ultra low or zero emission.
Controlling the temperature of the combustion by the air and steam injection, the formation of nox and other pollutants is virtually eliminated.
Even the friction loss of the piston is transformed as heat in the cylinder liner and is then, by thermal combustion, transferred back to the working fluid and recovered by the internal cooling air of regeneration and the steam of cogeneration.
The fuel injection and the water injection are preferably accomplished by a novel concept of a sequential, common rail injection system. The injection system advantageously works in conjunction with the total energy, triple thermal cycle to minimize both thermal and mechanical losses in high pressure engine systems, or in other systems where high pressure, hydraulic pumping systems result in losses in overall engine efficiency.